The invention relates to a method for preparing benzoxazinone and to the use of the prepared benzoxazinone.
Benzoxazinones may be used for the stabilisation of polymers against the degradative effects of light, as described in U.S. Pat. No. 4,446,262 or U.S. Pat. No. 3,989,698. The described methods for preparing benzoxazinone result in a benzoxazinone of some noticeable undesirable properties, either imparting high degree of colour to clear plastics, which limits their use to certain applications, or having a high concentration of sodium ions.
U.S. patent application 2003/0096889 A1 describes a method for preparing benzoxazinones. The method uses the reaction of recrystallised isatoic anhydride (ISA) with an acylating compound in the presence of pyridine, preferably anhydrous pyridine. The method requires the recrystallisation of the ISA, in order to remove coloured contaminants from the ISA, which would otherwise contaminate the final product. The recrystallisation step adds to the complexity of the method. Also, recrystallisation results in loss of raw material, imparts extra costs (extra solvent, equipment) and is undesired from an environmental point of view (incineration).
It is an object of the invention to provide a novel method for preparing a benzoxazinone, that can be used as an alternative to known methods.
In particular it is an object of the invention to provide a method which overcomes one or more of the drawbacks from which known methods may suffer, as described above.
More in particular it is an object of the invention to provide a method for preparing a benzoxazinone which allows the preparation of a benzoxazinone with a low yellow index and/or a low sodium concentration, especially also if commercially available ISA, in particular technical grade ISA is used that is not further purified by recrystallisation or otherwise prior to reaction with the acylating compound.
It has now been found that a benzoxazinone can suitably be prepared in the presence of a specific amine.